1. Field of the Invention
The present invention relates generally to RF (Radio Frequency) IC (Integrated Circuit) designs, and more particularly to a circuit and a method for implementing frequency tripled I/Q signals in a broadband wireless communication system.
2. Description of Related Art
Currently, planning and technical standards for millimeter-wave bands such as IEEE 820.15.3c are under development, which could be applied in various types of commodities requiring short-distance high-speed communications in the future, such as HDMIs, high speed wireless data transmissions, vehicle collision warning radars and imaging techniques.
Therein, if voltage-controlled oscillators (VCO) are directly used in millimeter-wave bands for generating local oscillating signals, phase noises of the VCOs would be serious. Therefore, in general, voltage-controlled oscillators at lower frequency are used in combination with frequency multipliers so as to provide high frequency oscillating signals. Further, recent communication systems often require I/Q signal sources for frequency conversion. However, high frequency signal sources are difficult to design due to poor component quality. Accordingly, frequency multipliers can be utilized with lower frequency signal sources for frequency synthesis, thereby reducing the burden of PLLs (Phase-Locked Loop).
At present, a main method of generating a frequency multiplied signal involves making a transistor operate at a strong non-linear area so as to output a square wave and further filtering the square wave by a filter so as to obtain a signal with a desired frequency. However, such a method consumes great power and amplitudes of input signals must be high such that transistors can operate at a strong non-linear area, which accordingly lowers the efficiency.
Therefore, how to provide a circuit and a method for implementing frequency tripled I/Q signals in a broadband wireless communication system which eliminates the requirement for high amplitude of input signals and has a broader bandwidth and lower power consumption and can be used in any processes has become urgent.